Mitigation of nitrate, nitrous oxide, and ammonia loss with time and source of nitrogen application in corn

The large need of nitrogen (N) for crop production and the negative impacts of fertilizer on the environment result in a compelling need to identify new or advanced N management practices to reduce N losses while maintaining productivity and profitability. Nitrate (NO₃) leaching, nitrous oxide (N₂O) denitrification, and ammonia (NH₃) volatilization are the most common pathways of N loss when synthetic N fertilizer is applied in agricultural lands. The objectives of this 7-year study (2014-2020) were to evaluate the use of traditional management practice (urea applied at pre-plant) and advanced N management practices [controlled-release fertilizer (ESN) and split applications with a urease inhibitor] on i) N losses (NO₃, N₂O, and NH₃); ii) corn yield and profitability; and iii) cropping system N balance including plant N removal and soil N status. Integration of all the variables measured into a N balance calculation showed to be a poor approach to estimate N efficiency or impact on environmental quality because plant N uptake overshadow treatment influence on N loss measurements.  Our findings indicate that pre-plant ESN can be considered a strategy to reduce N losses while maintaining crop yield. While split treatments increased corn yield, they did not reduce N losses, which contrasts the common assumption held by many that split applications are better for the environment. Nonetheless, the traditional management practice of pre-plant urea was the least efficient, producing lower crop yields and increasing N losses compared to pre-plant ESN in wet years. This demonstrates that there are N management practices that can improve production and environmental protection and their merit should be explored and refined further.